Testing a Conditional Form of Exogeneity

We give two new approaches to testing a conditional form of exogeneity. This conditionensures unconfoundedness and identication of eects of interest in structural systems. Asthese approaches do not rely on the absence of causal eects of treatment under the null,they complement earlier methods of Rosenbaum (1987) and Heckman and Hotz (1989)....